Prior to applicant's inventions U.S. Pat. Nos. 6,371,567 and 6,585,326, commercially usable bit holders as a part of bit holder assemblies, including a removable bit, a removable bit holder and a bit block mounted on a rotating drum for use mainly in road milling equipment were either mounted on bit blocks by use of a threaded nut or retaining clip, or, if not utilizing such a fastener, had a much shorter field use life than the quick change system described in those patents. Even with the continuing development of applicant's quick change bit assemblies, commercial users of the road milling, trenching and mining equipment have pressed for increased efficiency in bit holder changing operations to minimize the down time and maximize the useful operating life of road milling and other machinery utilizing these bit assemblies.
With the increased working life of the bit assemblies of applicant's prior inventions, there came a need to bulk up the structure of the bit holders to take the increased wear accompanying longer use life. Applicant's copending application Ser. No. 12/844,988 discloses an upper body portion of a bit holder which extends outwardly from the top of the bit block that retains the shank of the bit holder. This bit holder was shown in the application having an increased diameter upper body portion skirt whose bottom annular surface provided a base for a C-shape bit holder removal tool. The contents of that application are incorporated herein in total by reference.
Other assemblies and tools utilized for removal of bit holders from bit blocks are shown in applicant's prior U.S. Pat. Nos. 6,585,326; 7,883,155 and 8,069,544. Some of the prior tools utilized for removing bit holders cannot be used in instances where the bit, especially if coated with hard diamond material, is brazed onto the top of the bit holder the removal tools as described in U.S. Pat. Nos. 7,883,155 and 8,069,544 would not work in that instance. Additionally, users of applicant's equipment have indicated that bit holder removal tools that come in contact with the bit block during bit holder removal may result in degrading the outside of the bit block and would shorten longevity of the bit holder/bit block assembly useful life.
A need has developed for a bit holder upper body portion that is strong enough to have mounting slots therein capable of accepting a bit holder removal tool.
Additionally, a need has developed for a bit holder removal tool that when mounted on or adjacent a bit holder does not come in contact with the bit block.